Strongyloides stercoralis: antigenic analysis of infective larvae and adult worms

The protein composition of Strongyloides stercoralis infective larvae and adult worms solubilized sequentially in water, sodium deoxycholate and sodium dodecyl sulphate (SDS) and their excretory/secretory products were analysed by one- and two-dimensional SDS-polyacrylamide electrophoresis. These extracts were demonstrated to be complex mixtures containing many proteins, some of which were common and others which were stage-specific. Western blot analysis of these antigens with infected human sera showed most sero-reactivity against larval antigens, whilst normal human sera were unreactive. These data identify immunogenic antigens which may be available for detection in an antigen assay.     

Amphids in Strongyloides stercoralis and other parasitic nematodes

In this review, Francis Ashton and Gerhard Schad examine the ultrastructure of the amphids of several animal parasitic nematodes. These structures are the main chemosensory organs of these worms and probably play an important role in host-finding behavior and the control of development. Reconstructions made from serial micrographs of the neurons in the amphids of the threadworm Strongyloides stercoralis are shown. These stereo images permit three-dimensional visualization of these complex sense organs. The association between each amphidial neuron and its cell body has not been made previously for a parasitic nematode; however, this has been done for the free-living nematode Caenorhabditis elegans, which served as a model for these studies. Recognition of the cell bodies will provide a point of departure for laser microbeam ablation studies to determine individual neuronal function.     

A case of Strongyloides stercoralis infection.

Strongyloidiasis has been recognized as one of the life-threatening parasitic infections in the immunocompromised patients. We report an intestinal infection case of Strongyloides stercoralis in a 61-year-old man. Rhabditiform larvae were detected in the stool examination and developed to filariform larvae having a notched tail through the Harada-Mori filter paper culture. The patient received five courses of albendazole therapy but not cured of strongyloidiasis.     

Hyperinfective strongyloidiasis: Strongyloides stercoralis undergoes an autoinfective burst in neonatal gerbils

One of the unusual aspect of the life cycle of Strongyloides stercoralis is the occurrence of autoinfective third-stage larvae (L3a). These are the causative agents of severe hyperinfective strongyloidiasis. When 6-wk-old gerbils are infected with 1,000 infective third-stage larvae (L3i), no L3a are seen during the course of the infection. However, in neonatal gerbils (1-13 days of age) infected with 1,000 L3i, a burst of autoinfection takes place between 15 and 30 days postinfection (PI). Only occasional L3a can be found in neonatally infected gerbils after 4 wk PI. This autoinfective burst is not seen in neonatal gerbils infected with 200 L3i.     

Frequency of Strongyloides stercoralis infection in alcoholics

Several studies have shown that chronic alcoholics have increased susceptibility to infections due to higher exposure to infectious agents as well as breakdown in their immune defenses. As Strongyloides stercoralis infection is usually more relevant in immunocompromised patients, the aim of this study was to evaluate the frequency of S. stercoralis infection in alcoholics. Thus, coproparasitological examination was carried out in 145 subjects, from which 45 were chronic alcoholics (mean age of 45.7 +/- 11.0 years), 10 were nonalcoholic cirrhotic patients (mean age of 50.2 +/- 13.1 years), and 90 were asymptomatic nonalcoholic subjects (mean age of 46.7 +/- 10.1 years), which served as controls. From the alcoholics, 9 had hepatic cirrhosis, 9 had chronic pancreatitis and 27 had neither cirrhosis nor pancreatitis. For the diagnosis of strongyloidiasis, the Baermann-Moraes and Lutz methods were used in three fecal samples from each subject. Samples were collected at alternated days, and three slides of each sample were analyzed for each method, thus totalizing 2,610 slides examined. The frequency of strongloidiasis in the total alcoholic group (33.3%) and in the subgroups of alcoholics, i.e., patients with hepatic cirrhosis (44.4%), with chronic pancreatitis (33.3%), and those with no cirrhosis or pancreatitis (29.6%) was statistically higher than that found in the control group (5.5%). None of the individuals with nonalcoholic hepatic cirrhosis had S. stercoralis infection. Our results showed that the chronic alcoholism itself is an important factor that predisposes to strongyloidiasis.     

肿瘤移植裸鼠粪类圆线虫感染病原和分子诊断

目的：肿瘤移植裸鼠粪类圆虫病诊断。方法肿瘤移植裸鼠的尸体解剖显微镜检查发现类圆线虫作形态学鉴定并采用二重PCR进行分子诊断。结果尸检发现肿瘤移植裸鼠样本中出现大量粪类圆线虫,初步确诊粪类圆线虫病,二重PCR检出样本中粪类圆线虫特定DNA进一步确诊。结论防止这种严重后果是早期诊断。肿瘤移植受体和供体应进行寄生虫感染包括类圆线虫病筛查。本研究第一个广泛报道了肿瘤移植裸鼠粪类圆虫病诊断。     

Strongyloides stercoralis infection in former Far East prisoners of war.

Out of 602 consecutive people who had been prisoners of war in the Far East and were screened for tropical diseases, 88 (15%) were found to have Strongyloides stercoralis infection a mean period of 30 years after their return from the tropics. The classical strongyloid creeping eruption was the most common symptom (84%), while gastrointestinal disturbances were rare (5%). Thiabendazole was highly effective in eradicating the infection. Strongyloidiasis is an important condition, as when the host is immunosuppressed fatal hyperinfection may occur. Many undiagnosed cases of strongyloidiasis must exist among former prisoners of war, and it is thus important to identify and treat these patients.     

Efficacy of agar-plate culture in detection of Strongyloides stercoralis infection

Agar-plate culture of feces using a modified petri dish proved to be highly efficient in the detection of Strongyloides stercoralis infection. Furrows left by S. stercoralis on the agar plate were distinguished readily in size from those left by Necator americanus.     

Strongyloides venezuelensis: heparin-binding adhesion substances in immunologically damaged adult worms

Immunologically damaged Strongyloides venezuelensis adult worms were examined for their mucosal invasion ability and secretion of heparin-binding adhesion substances. S. venezuelensis was expelled from male Wistar rats 4 to 5 weeks after infection. Four-week-old adult worms were smaller and had fewer eggs than 1-week-old adult worms. One-week-old, 4-week-old, and 5-week-old adult worms equally established in the recipient mouse intestine when surgically implanted. Adult worms of 4 and 5 weeks of age secreted adhesion substances as much as 1-week-old adult worms. There was no difference in the heparin-binding activities and the lectin-binding profile of adhesion substances among adult worms of different ages. The rate of secretion of adhesion substances from the mouth was also identical. Heparin-binding activities were detected in crude adult worm proteins; however, proteins of 5-week-old adult worms had weaker heparin-binding activities than those of 1-week-old adult worms. Western blotting revealed that a number of heparin-binding proteins were lost in 5-week-old adult worms. A heparin-binding protein of 42. 0 kDa, which was consistently expressed in adult worms, was a possible component of heparin-binding adhesion substances which are secreted from the mouth.     

The neurons of class ALD mediate thermotaxis in the parasitic nematode, Strongyloides stercoralis

Strongyloides stercoralis, a skin-penetrating nematode parasite of homeotherms, migrates to warmth. In nematodes, the amphids, anteriorly positioned, paired sensilla, each contain a bundle of sensory neurons. In the amphids of the free-living nematode Caenorhabditis elegans, a pair of neurons, each of which ends in a cluster of microvilli-like projections, are known to be the primary thermoreceptors, and have been named the finger cells (class AFD). A similar neuron pair in the amphids of the parasite Haemonchus contortus is also known to be thermosensory. Strongyloides stercoralis lacks finger cells but, in its amphids, it has a pair of neurons whose dendrites end in a multi-layered complex of lamellae, the so-called lamellar cells (class ALD). Consequently, it was hypothesised that these lamellar cells might mediate thermotaxis by the skin-penetrating infective larva of this species. To investigate this, first stage S. stercoralis larvae were anaesthetised and the paired ALD class neurons were ablated with a laser microbeam. The larvae were then cultured to the infective third stage (L3) and assayed for thermotaxis on a thermal gradient. L3 with ablated ALD class neuron pairs showed significantly reduced thermotaxis compared with control groups. The thermoreceptive function of the ALD class neurons (i) associates this neuron pair with the host-finding process of S. stercoralis and (ii) demonstrates a functional similarity with the neurons of class AFD in C. elegans. The structural and positional characteristics of the ALD neurons suggest that these neurons may, in fact, be homologous with one pair of flattened dendritic processes known as wing cells (AWC) in C. elegans, while their florid development and thermosensory function suggest homology with the finger cells (AFD) of that nematode.     

Role of IL-5 in innate and adaptive immunity to larval Strongyloides stercoralis in mice

Protective immunity to Strongyloides stercoralis infective larvae in mice has been shown to be dependent on IL-5 based on mAb depletion studies. The goal of this study was to determine the functional role of IL-5 during the innate and adaptive immune response to larval S. stercoralis in mice. In these studies, three strains of mice were used: wild-type C57BL/6J (WT), IL-5 knockout (KO), and IL-5 transgenic (TG). Innate responses to the larvae indicated that there was enhanced survival in the KO animals and decreased survival in the TG animals compared with WT. Furthermore, killing of larvae in TG mice was associated with eosinophil infiltration and degranulation. In studying the adaptive immune response, it was observed that immunization of KO mice did not lead to the development of protective immunity. Experiments were then performed to determine whether KO mice reconstituted with Abs or cells could then develop protective immunity. KO mice displayed protective immunity via a granulocyte-dependent mechanism following injection of purified IgM from immune wild-type animals. Immunity in KO mice could also be reconstituted by the injection of eosinophils at the time of immunization. These eosinophils did not participate in actively killing the challenge infection, but rather were responsible for the induction of a protective Ab response. We conclude that IL-5 is required in the protective immune response for the production of eosinophils, and that eosinophils were involved in larval killing during innate immunity and in the induction of protective Abs in the adaptive immune response.     

Protease resistant interleukin-3 stimulating components in excretory and secretory products from adult worms of Strongyloides ratti.

Excretory and secretory (ES) products collected from adult worms of Strongyloides ratti stimulated interleukin-3 (IL-3) production with mesenteric lymph node cells from infected C57BL/6 mice, but not with normal mesenteric lymph node cells. The IL-3 stimulating components were not major IgG binding antigens. Activity of the IL-3 stimulating components was stable by treatment with protease, although reduced by heating in boiling water.     

Strongyloides ratti: the role of interleukin-5 in protection against tissue migrating larvae and intestinal adult worms

To determine the role of interleukin-5 (IL-5) and eosinophils in protection against Strongyloides ratti, mice treated with anti-IL-5 monoclonal antibody (mAb) were infected with S. ratti larvae. Strongyloides ratti egg numbers in faeces (EPG) in mAb treated mice were higher than those in control mice on days 6 and 7 after inoculation. The numbers of migrating worms in mAb treated mice 36 h after inoculation were higher than those observed in control mice. Intestinal worm numbers in mAb treated mice 5 days after inoculation were higher than those in control mice. These results show that eosinophils effectively protected the host against S. ratti infection by mainly the larval stage in primary infections. The involvement of eosinophils in protection against secondary infection was also examined. Before secondary infection, mice were treated with anti-IL-5 mAb and infected with S. ratti. Patent infections were not observed in either mAb treated or control Ab treated mice. The numbers of migrating worms in the head and lungs of mAb treated mice increased to 60% of that in primary infected mice. Intestinal worms were not found in mAb treated mice or in control mice after oral implantation of adult worms. Eosinophils were therefore mainly involved in protection against tissue migrating worms in secondary infections.     

Alcoholism and Strongyloides stercoralis: Daily Ethanol Ingestion Has a Positive Correlation with the Frequency of Strongyloides Larvae in the Stools

Background

Significantly higher prevalence of Strongyloides stercoralis has been reported in chronic alcoholic patients. The aim of this investigation was to report the prevalence of Strongyloides larvae in stools of chronic alcoholic patients with known daily ethanol intake.

Methods

From January 2001 through December 2003 the results of fecal examinations and the daily ethanol intake were retrieved from the records of 263 chronic alcoholic and from 590 non-alcoholic male patients that sought health care at the outpatients unit of the University Hospital C A Moraes. Alcoholic patients were separated into four groups, with 150g intervals between the groups according to the daily ethanol intake.

Results

(a) The frequency of Strongyloides was significantly higher in alcoholic patients than in control group (overall prevalence in alcoholic 20.5% versus 4.4% in control group; p = 0.001). Even in the group with a daily intake of ethanol equal to or less than 150g the prevalence was higher than in control group, although non significant (9.5%, versus 4.4% in control group; p = 0,071); (b) the prevalence of Strongyloides in alcoholic patients rises with the increase of ethanol intake (Pearson''s Correlation Coefficient = 0.956; p = 0.022), even in patients without liver cirrhosis (Pearson''s Correlation Coefficient = 0.927; p = 0.037).

Conclusion

These results confirm and reinforce the hypothesis that chronic alcoholism is associated with Strongyloides infection, which is in direct relationship with the severity of alcoholism, independently of the presence of liver cirrhosis.